Thymosin alpha 1 (Tα1) is one of the active peptides secreted by thymus gland, and has highly conserved sequence and the Tα1 from different species has the same chemical structure. Tα1 is consisted of 28 amino acid residues, having a molecular weight of 3108 and an isoelectric point of 4.2, and it's N-terminal is acetylated. The primary structure of Tα1 is:
    1                                  10Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-                                 20Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-                 28Glu-Glu-Ala-Glu-Asn-OH
Tα1 is known as an immunopotentiator to T lymphocytes and it can promote T cell maturation and differentiation, induce mature T cell secreting several lymphokines (such as interleukin-2 and interferon-γ), and induce the generation of interleukin-2 receptor. In addition, Tα1 has direct inhibiting or killing effect on the growth of some virus infected cells and tumor cells. As for immunopotentiator, Tα1 is effective in treating diseases related to immune deficiency or hypoimmunity. Clinical trail for Tα1 started at 1980's. Tα1 is also effective and safe in treating chronic hepatitis B when is used alone or in combination with interferon. For several other diseases such as hepatitis C, hepatoma, malignant melanoma, non-small cell lung cancer, and HIV etc., Tα1 is also effective. Moreover, Tα1 can be used as vaccine supplement to increase the effect of influenza and hepatitis B vaccine.
Tα1 currently used in clinical is a synthetic chemical as a formulation of sterilized dry powder. The dosage for the treatment of chronic hepatitis B is 1.6 mg per dose for twice one week by injecting 2, and the course of treatment is 6 months. This treatment has shortcomings such as high-dose, frequently injections and high cost. So it is important to improve the metabolism of Tα1 in vivo, to increase the bioavailability, to prolong the effectiveness and to find long-acting Tα1 analogues.